A NEUTRAL GALACTOCEREBROSIDE SULFATE SULFATIDASE FROM MOUSE-BRAIN

We have described an enzyme in brain that catabolizes galactocerebrosi de sulfatide with a pH optimum of 7.2. To our knowledge, this is the f irst description of a catabolic enzyme for sulfatide at a neutral pH, Activity at a neutral pH implies a non-lysosomal location for this sul fatidase. Galactocerebroside sulfate sulfatidase (n-sulfatidase) activ ity was not apparent in crude microsomal extracts acid was detected fo llowing partial purification of the enzyme, This enzyme, n-sulfatidase , differs from other arylsulfatases in its M(r), inability to bind to concanavalin A, and substrate specificity; n-sulfatidase was unable to hydrolyze p-nitrocatechol sulfate or estrone sulfate, The molecular m ass of n-sulfatidase obtained by Sephacryl S-200 chromatography was 72 kDa, and the active fraction from this procedure was purified >600-fo ld by isoelectric focusing. Following SDS polyacrylamide gel electroph oresis, two bands were obtained with apparent molecular masses of 58 a nd 66 kDa, Enzyme activity was regenerated from both of these bands, w ith the 66-kDa band showing greater activity, The K-m of the sulfatida se was determined as 5.8 x 10(-5) M. The pI of n-sulfatidase was 7.7 i n contrast to the pI of 4.9 for the sulfotransferase. No requirement w as found for Mg2+ or ATP for sulfatidase activity; vitamin K-1 enhance d sulfatidase activity approximately 3.3-fold. Therefore, this enzyme may have a role in the pathogenesis of metachromatic leukodystrophy in which sulfatides accumulate in the nervous and other tissues and in m yelination since sulfatides are an important component of myelin.